<template>
  <transition mode="out-in" v-on="on">
    <slot></slot>
  </transition>
</template>
<script lang="ts">
  import { defineComponent } from "vue";
  import { addClass, removeClass } from "@mfish/core/utils/DomUtils";

  export default defineComponent({
    name: "MenuCollapseTransition",
    setup() {
      return {
        on: {
          beforeEnter(el) {
            addClass(el, "collapse-transition");
            if (!el.dataset) el.dataset = {};

            el.dataset.oldPaddingTop = el.style.paddingTop;
            el.dataset.oldPaddingBottom = el.style.paddingBottom;

            el.style.height = "0";
            el.style.paddingTop = 0;
            el.style.paddingBottom = 0;
          },

          enter(el) {
            el.dataset.oldOverflow = el.style.overflow;
            if (el.scrollHeight === 0) {
              el.style.height = "";
              el.style.paddingTop = el.dataset.oldPaddingTop;
              el.style.paddingBottom = el.dataset.oldPaddingBottom;
            } else {
              el.style.height = `${el.scrollHeight}px`;
              el.style.paddingTop = el.dataset.oldPaddingTop;
              el.style.paddingBottom = el.dataset.oldPaddingBottom;
            }

            el.style.overflow = "hidden";
          },

          afterEnter(el) {
            removeClass(el, "collapse-transition");
            el.style.height = "";
            el.style.overflow = el.dataset.oldOverflow;
          },

          beforeLeave(el) {
            if (!el.dataset) el.dataset = {};
            el.dataset.oldPaddingTop = el.style.paddingTop;
            el.dataset.oldPaddingBottom = el.style.paddingBottom;
            el.dataset.oldOverflow = el.style.overflow;

            el.style.height = `${el.scrollHeight}px`;
            el.style.overflow = "hidden";
          },

          leave(el) {
            if (el.scrollHeight !== 0) {
              addClass(el, "collapse-transition");
              el.style.height = 0;
              el.style.paddingTop = 0;
              el.style.paddingBottom = 0;
            }
          },

          afterLeave(el) {
            removeClass(el, "collapse-transition");
            el.style.height = "";
            el.style.overflow = el.dataset.oldOverflow;
            el.style.paddingTop = el.dataset.oldPaddingTop;
            el.style.paddingBottom = el.dataset.oldPaddingBottom;
          }
        }
      };
    }
  });
</script>
